A high performing, low risk and low cost monopropellant is the most attractive concept for chemical propulsion. A monopropellant will require a minimum of components to build up a propulsion system and thus will lead to minimum complexity and minimum cost.
The dominating monopropellant for spacecraft propulsion is hydrazine. The major advantages of hydrazine systems are long flight heritage and well-established technology. The major drawbacks of hydrazine systems are the hazards involved. Hydrazine is highly toxic and carcinogenic and hence, rigorous routines are required for manufacturing, handling and operation of hydrazine systems.
Due to hazards, and therefore the total cost, an alternative propellant is highly attractive. Thus, hydrazine will sooner or later be replaced due to cost reduction, safer handling and new requirements on personal safety and environmental requirements. However, this requires that the alternative propellant reach maturity and has been flight qualified.
As indicated above, hydrazine is today widely used as a monopropellant for space applications, but unfortunately it is very toxic, making it hard and expensive to handle. Thus new, less toxic monopropellants are desired.
Ammonium dinitramide (ADN) is a new solid oxidizer, mainly intended for high performance composite rocket propellants. ADN and other similar compounds are the subject of several patents for application as solid composite rocket propellants and as explosives, both for pyrotechnic applications in general and for other uses, such as in inflators for air-bags. The composite explosives of this type typically comprise ADN (or some other compound) as an oxidizer, an energetic binder (e.g. energetically substituted polymers), a reactive metal and other typical propellant ingredients such as curatives and stabilizers. One of the disadvantages of ADN, as a solid oxidizer, is its high hygroscopicity.